GEOCHEMICAL CORRELATION OF AUSTRALIAN CRUDE OILS

Abstract

Correlation of crude oils with either their suspected source rocks or other crude oils thought to be derived from similar sources is important for basin studies and their suspected source rocks or other crude oils thought to be derived from similar sources is important for basin studies and and source rock extracts using computerized gas chromatography — mass spectrometry (C-GC-MS). Biological markers are compounds that retain the structure of molecules occurring in living organisms during diagenesis and conversion of the original organic material to petroleum hydrocarbons. In general, the distribution of biological markers is identical for oils from similar sources and for their respective source rocks. Differences in sources or maturity of the oils lead to differences, sometimes very subtle, in the distribution of the biological markers.

Results from C-GC-MS analyses performed on a series of oils from the Gippsland, Carnarvon and Surat Basins show how two classes of biological markers, namely steranes and triterpanes, can be used for correlation purposes. Oils from the Gippsland Basin can be divided into two groups differing in source and maturity. Similarly, the oils examined from the Dampier Sub-basin fall into two groups. It is proposed that they have at least one common source, with one group being distinguished by the presence of additional source material. Additional data are presented to show that the Barrow Jurassic and Windalia oils are derived from the same or similar sources and differ only as a result of the biodegradation of the Windalia oil. Results for the limited number of oils examined from the Surat Basin suggest the presence of at least two sources for the oils of this basin.